ICDs are implantable devices adapted to automatically detect and interrupt rapid, irregular atrial and/or ventricular heart muscle contractions. ICDs typically deliver a high energy and voltage electrical shock to the heart upon detection of an arrhythmic event, such as fibrillation, to override the electrochemical conduction and enable the heart to resume normal rhythm. However, the high energy and voltage shocks delivered by ICDs can cause significant pain to the patient and pain control remains a major issue in ICD therapy.
The pain felt by the patient upon delivery of a shock from the ICD causes moderate to severe physical and psychological trauma. Atrial fibrillation reduces cardiac efficiency, but is not generally lethal, at least on a short term basis. Pain is a major issue limiting the success of high voltage atrial fibrillation (AF) therapies in the patients that are unwilling to tolerate pain for something that was not immediately lethal. Thus, it would be very attractive to have additional techniques to deal with pain for atrial fibrillation.
An additional problem that is often not recognized is how serious the pain issue is for patients with ventricular arrhythmias which can be immediately lethal unless terminated. Even though many patients have no viable alternative other than to accept the pain because the alternative is death, the pain issue causes many patients significant physical and emotional distress.
The pain of the shocks is generally due to two sources: First, inappropriate shocks resulting from a misdiagnosis of or for non-sustained lethal arrhythmias. A misdiagnosis occurs when the device incorrectly detects an arrhythmia and delivers a shock when the patient is not in fact experiencing an arrhythmia that would indicate a shock. A non-sustained arrhythmia in this context is an arrhythmia that self-terminates and can result in inducing the device to appropriately prepare a shock and inappropriately deliver the shock even though the potentially lethal arrhythmia has terminated. In these cases, the patient may be fully conscious to feel the full pain of an inappropriate shock.
The second problem is that rapidly charging devices can deliver the shock while the patient is still conscious in about one third of all cases. This is advantageous as it can eliminate some sequelae due to car accidents, falls, etc., but the patient is conscious so as to feel the full pain of the shock.
The use of rounded waveforms can reduce the pain of the shock as can possible nerve stimulus blocking. However, neither of these measures alone or even in conjunction is generally adequate to eliminate the shock pain or even make it completely tolerable.
Hypnosis has long been used for the control of mild to severe pain. In fact, before the discovery of ether and chloroform in the 1840s, it was one of the few methods available for surgical anesthesia. Careful studies have shown that hypnotizable subjects can reduce pain perception by 3 to 4 points on the classic 10-point pain scale. This is a significant reduction even greater than what would be expected with the use of rounded shock waveforms, for example. Different people have different levels of hypnotic inducibility. It is found that at least 80% of psychologically normal patients are at least somewhat hypnotically inducible. Even those patients that would not be considered clinically inducible can benefit from hypnotic pain reduction. Hypnotic pain reduction is a demonstrable physiological occurrence and can be observed by reduced brainwave response to painful stimuli.
From the foregoing, it will be understood that there is an ongoing need for a system that alleviates a patient's sensation of pain under ICD shocks for both atrial and ventricular arrhythmia treatments. There is a further need to provide this alleviation while maintaining the capability, where possible through rapid charging, to deliver shocks as rapidly as possible to avoid sequelae that may occur if a delay in shocking would lead to unconsciousness.